Medical apparatus

ABSTRACT

The present invention relates to a medical apparatus which includes a motion mechanism which has at least one degree of freedom, an actuator configured to drive the motion mechanism and a control unit configured to control the actuator, and which operates in a magnetic field environment of an MRI, the medical apparatus including: a data storage unit in which data related to magnetic susceptibility of the actuator is stored; a calculating unit configured to calculate information related to an influence which the actuator exerts upon the magnetic field environment by calculation based on the magnetic susceptibility; and a communication unit configured to output the information to the MRI. An influence which an apparatus which operates in a strong magnetic field environment exerts upon an MR image can be reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending U.S. patent applicationSer. No. 14/407,058, filed Dec. 10, 2014, which is a U.S. national stageapplication of International Patent Application No. PCT/JP2013/064961filed May 22, 2013, which claims foreign priority to Japanese PatentApplication No. 2012-135449, filed Jun. 15, 2012. All of the aboveapplications are hereby incorporated by reference herein in theirentirety.

TECHNICAL FIELD

The present invention relates to a medical apparatus which is operatedunder an environment under which a strong magnetic field is used, suchas a magnetic resonance imaging apparatus.

BACKGROUND ART

A magnetic resonance imaging (MRI) apparatus provides a static magneticfield and a specific high frequency magnetic field to a measurement siteof a subject, and makes an image of the inside of measurement site byapplying a nuclear magnetic resonance phenomenon caused inside themeasurement site.

PTL 1 discloses a visual stimulus presentation system for measuring acerebral function using an MRI having a specific function calledfunctional MRI. The disclosed visual stimulus presentation systemincludes an actuator which moves within a bore of an MRI apparatus.

NPL 1 discloses a method of puncture operation and a puncture devicesystem using an MRI.

CITATION LIST Patent Literature

-   PTL 1 Japanese Patent Laid-Open No. 2011-245202

Non Patent Literature

-   NPL 1 “Compact Manipulator System for Guiding Needle with Real-time    Navigation Based on MR Images” Journal of Japan Society of Computer    Aided Surgery Vol. 9 (2): 91-101, 2007

SUMMARY OF INVENTION Technical Problem

In a related art technology, there has been a possibility that, when anMRI-compatible medical apparatus, such as an actuator, is disposed undera magnetic field environment, an influence upon an MR image is notsufficiently reduced.

Usually, titanium which is used as a component of a medical apparatus isgenerally considered as a nonmagnetic material. To the MRI, however,titanium is not necessarily a nonmagnetic material. This is becausetitanium has enough magnetic susceptibility to affect the MR image(about 180 parts per million (ppm)). Therefore, it is desirable that themedical apparatus is made of material having magnetic susceptibilitysmaller than that of titanium by at least one order (ideally, the samemagnetic susceptibility as that of water, i.e., −9 ppm). However, evenif the medical apparatus is made of a material which sufficientlysatisfies requirements of nonmagnetism for the MRI, there are stillcomponents and parts that are not able to satisfy necessary functions bythe material. For example, even if an influence upon the image may beavoided as much as possible by forming a mechanism element of the armusing resin, it is generally difficult to make a common actuator, suchas a motor, using resin (except for particular cases includingartificial muscle). Therefore, as long as the related art medicalapparatus is disposed and is made to operate in the bore of the MRIwhich is the strong magnetic field environment, it is practicallydifficult to completely remove the influence upon the MR image in ahardware aspect.

Solution to Problem

The present invention provides a medical apparatus which reduces aninfluence which the medical apparatus exerts upon an MR image when themedical apparatus is operated in a strong magnetic field environment andwhich is compatible with the strong magnetic field environment.

The present invention provides a medical apparatus which includes amotion mechanism which has at least one degree of freedom, an actuatorconfigured to drive the motion mechanism and a control unit configuredto control the actuator, and which operates in a magnetic fieldenvironment, the medical apparatus including: a data storage unit inwhich data related to magnetic susceptibility of the actuator is stored;a calculating unit configured to calculate information related to aninfluence which the actuator exerts upon the magnetic field environmentby calculation on the basis of the magnetic susceptibility; and acommunication unit configured to output the information to an externaldevice.

Advantageous Effects of Invention

According to the present invention, in a medical apparatus, such as amedical manipulator, used in combination with an external device(external medical equipment) which uses a strong magnetic fieldrepresented by an MRI, it is possible to perform precise imagecompensation by outputting, to the external device, compensationinformation on the basis of an influence of the magnetic fielddistortion caused by the existence of the medical apparatus in themagnetic field so that the external device can use the compensationinformation. Then, as the precision of the captured image is increased,the precision of diagnosis is also increased.

Further, it is possible to perform real-time image compensation on theexternal device side depending on the status of the dynamically changingmedical apparatus by performing calculation about compensationinformation each time a position and a posture of the medical apparatuschange, and outputting the updated calculation result to an externaldevice via a communication unit.

Further, since image compensation can be carried out by software-basedprocess depending on a configuration of the medical apparatus, a medicalapparatus with high versatility can be provided.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1C are schematic diagrams illustrating an exterior of an MRIapparatus according to the present invention.

FIGS. 2A and 2B are schematic diagrams illustrating a configuration of amedical apparatus according to the present invention.

FIG. 3 is a block diagram illustrating a configuration of a medicalapparatus according to the present invention.

FIGS. 4A and 4B are explanatory views illustrating a concept ofapproximation of a ring-type USM using spheres according to the presentinvention.

FIG. 5 is an analysis diagram illustrating a magnetic field analysisresult by sphere approximation according to the present invention.

FIG. 6 is a block diagram illustrating a configuration of anothermedical apparatus according to the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings. The following embodiments do not limit thepresent invention related to the claims and not all the combinations offeatures described in the embodiments are necessary to the means forsolving the present invention.

First Embodiment

FIGS. 1A to 1C are schematic diagrams illustrating an exterior of an MRIapparatus. FIG. 1A is a horizontal cross-sectional view, FIG. 1B is afront view and FIG. 1C is a side sectional view. A bore 21 which is anexamination space of an MRI includes a circular opening. Usually, asubject (e.g., a human body) 23 is disposed on an examining table 22 ina lying position (the human body 23 is not illustrated except for thehorizontal cross-sectional view of FIG. 1A). In the horizontalcross-sectional view of FIG. 1A, the direction from the leg toward thehead of the human body 23 corresponds to the forward direction of a zaxis in the coordinate. This direction is equivalent to the direction ofthe static magnetic field of an MRI 20. The MRI apparatus includes animage processing unit (not illustrated) which receives nuclear magneticresonance signals issued by the subject 23 and generates image signalsfor causing an MR image inside the subject on the basis of the nuclearmagnetic resonance signals to be displayed. The image processing unitcompensates the image signals on the basis of information transmittedfrom the later-described medical apparatus which operates in a magneticfield environment inside the bore 21 (i.e., information related to aninfluence which the actuator of the medical apparatus exerts upon themagnetic field environment). The image signals consist of coordinates ofthe pixel which constitute the MR image and a pixel value. The imageprocessing unit compensates for the coordinates of the image signals onthe basis of the information related to an influence which the actuatorexerts upon the magnetic field environment. Since detailedconfigurations and the principle of operation of the MRI apparatus arepublicly known techniques, description thereof will be omitted.

FIGS. 2A and 2B are schematic diagrams illustrating a schematicstructure and exemplary installation of the medical apparatus in thebore 21. FIG. 2A is a plan view illustrating only a medical apparatusportion and FIG. 2B is a front view illustrating the inside of the bore21 seen from the leg side of the human body 23. An inner-bore disposedportion 30 of the medical apparatus which is disposed inside the bore 21includes a puncture needle storage unit 42 in which a puncture needle 43is stored, a driving mechanism unit 41 in which a power transmittingunit 44 and an actuator 10 which drives the puncture needle 43 via thepower transmitting unit 44 are stored, and an arm unit 40 which performsfixation and positioning of the driving mechanism unit 41 with respectto an examining table 22. As the actuator 10, an oscillatory-typeactuator which uses no magnet, especially a ring-type ultrasonic motor(USM) is used. Since the principle of motion and the driving method andthe like of the USM are publicly known techniques, description thereofwill be omitted. By constituting components other than the actuator 10by nonmagnetic materials, such as high intensity resin, it is possibleto consider that the actuator 10 is the only element that is affectingthe MR image.

FIG. 3 is a block diagram illustrating a configuration of the medicalapparatus. It is possible to consider that the medical apparatus is arobotics system which operates under a magnetic field environment andhas at least one degree of freedom. The system is divided into twoblocks: a block disposed inside the bore 21 (i.e., the inner-boredisposed portion 30) is illustrated by a dotted line. Another block isdisposed outside the bore 21. The MRI 20 illustrated as a double frameis an external device. A control unit 12 controls, using existing PIDcontrol, the actuator 10 for carrying out position control of an motionmechanism 11 constituted by the power transmitting unit 44 and thepuncture needle 43 in accordance with an operating command output froman unillustrated command output unit. The motion mechanism 11 is amechanism which has at least one degree of freedom including a verticalmovement of the puncture needle 43 (i.e., a motion to cause the punctureneedle 43 to be taken out of the puncture needle storage unit 42 and amotion to cause the puncture needle 43 to be drawn in the punctureneedle storage unit 42). Position information about the puncture needle43 detected by an unillustrated position detector is input in thecontrol unit 12 and, on the basis of the input position information,feedback control of the motion of the puncture needle 43 is carried out.The control unit 12 outputs the position information about the punctureneedle 43 to a compensation information calculating unit 4 sequentially.A position detecting unit 1 in which an optical sensor is used detectsthe position of the actuator 10 and outputs the position information tothe compensation information calculating unit 4. A posture detectingunit 2 in which a gyro sensor is used detects a posture of the actuator10 and outputs posture information to the compensation informationcalculating unit 4. A data storage unit 3 at least stores informationrelated to magnetic susceptibility of the actuator 10 (e.g., therelative permeability, the volume, an external magnetic field andpositional coordinates). A data storage unit 3 also stores in advancedata necessary for calculation of compensation information, e.g., dataregarding forms and data regarding magnetic susceptibility of eachcomponent of the inner-bore disposed portion 30. The communication unit5 functions as an I/O interface between the compensation informationcalculating unit 4 and the MRI 20. The compensation informationcalculating unit 4 calculates compensation information which should betransmitted to the MRI 20 in accordance with various types ofinformation obtained from each unit (i.e., the position detecting unit1, the posture detecting unit 2, the data storage unit 3, thecommunication unit 5 and the control unit 12) and outputs the calculatedcompensation information to the communication unit 5. The compensationinformation calculating unit 4 repeats the calculation each time when atleast one piece of information input from each the above-described unitsis updated, and each time outputs compensation information which isnewly obtained calculation result to the MRI 20 via the communicationunit 5.

Operation of the compensation information calculating unit 4 andtransmission/reception of information between the MRI 20 will bedescribed.

The basic content of the compensation information is, regarding at leasta part of the inner-bore disposed portion 30 (hereafter, referred to asan object A), three-dimensional space distribution (magnetic fielddistribution information) inside the bore 21 of the magnetic field whichan object A generates under an influence of the magnetic field of theMRI 20. As the object A, the actuator 10 is assumed because it isdifficult to constitute the actuator 10 only by materials that do notaffect an MR image, such as resin. That is, the magnetic fielddistribution information is information related to an influence whichthe actuator 10 exerts upon the magnetic field environment. Precision ofMR images is increased by using such information for image generation,because the image reconstruction algorithm of the MRI 20 determines thecoordinates of image information using magnetic field distribution.

Here, the image reconstruction algorithm will be described briefly. Thez-coordinate of the image is a section of the human body 23 in thedirection extending the head and the legs, i.e., determining the slicingposition. It is determined in accordance with the magnetic fielddistribution in the z axial direction. And then, the x-coordinate of theimage is determined by performing frequency encoding using the gradientmagnetic field in the x axial direction. This uses a physical phenomenonthat the resonant frequency of the nuclear magnetic resonance spin isproportional to the field strength, and so the frequency distribution inthe x axial direction is proportional to a gradient magnetic field inthe x axial direction. Further, the y-coordinate of the image isdetermined by performing phase encoding which provides skeweddistribution to the phase of the nuclear magnetic resonance spin inaccordance with the gradient magnetic field in the y axial direction.The phase encoding will be described briefly. First, the same gradientmagnetic field as in the x axial direction makes the nuclear magneticresonance spin have a gradient distribution of frequency for a certainperiod of time in the y axial direction. Then, although the resonantfrequency also returns when gradient magnetic field is returned to theoriginal, since the resonant frequency had a gradient (distribution) bythe certain period of time, the phase of the nuclear magnetic resonancespin has been shifted linearly along the y-axis in accordance with thegradient magnetic field strength. The coordinates of the image aredetermined on the basis of the frequency and the phase encodingdescribed above. At this time, to obtain stable images, it is requiredthat the magnetic field has homogeneity and linearity in the order ofppm.

Next, a case in which the object A exists in the bore 21 and, thereby,distribution of the static magnetic field is not homogenous anddistortion exists will be considered. Regarding the x axial directionand the z axial direction, the same distortion exists also in thedistribution of the gradient magnetic field and the coordinates of theimage are displaced in proportion to the distortion. Regarding the yaxial direction, when a phase rotation angle produced by the phaseencoding is changed in proportion to the distortion of the gradientmagnetic field, the coordinates on the image are displaced. Then, byusing the magnetic field distribution information about the object A asthe compensation information, it is possible to compensate for picturedistortion due to displacement of the pixel (i.e., the pixel and thevoxel) in the image reconstruction algorithm on the MRI 20 side and toreduce an influence upon the MR image due to existence of the object Ain the bore 21.

The compensation information calculating unit 4 may receive informationabout an imaging slice position, field of view (FOV), the staticmagnetic field, and the like from the MRI 20 as parameters about theexternal device via the communication unit 5. The compensationinformation calculating unit 4 may calculate compensation informationusing these parameters, thereby minimizing the calculation amount.

Various methods are known as methods for calculating spatialdistribution of the generated magnetic field which is generated by theobject A. However, it requires long time for updating the data toanalyze the magnetic field with high precision using a method such as afinite element method. Therefore, it is desirable to reduce thecalculation amount as much as possible using approximation in a range inwhich a sufficient compensation effect is obtained.

Hereinafter, the method for approximation in a case in which theactuator 10 is a ring-type USM will be described.

FIGS. 4A and 4B are explanatory views schematically illustrating aconcept of a method for approximating the ring-type USM with a pluralityof spheres. FIG. 4A illustrates a ring model 10′ in which the ring-typeUSM is considered as a simple torus shape (i.e., a toroidal shape). FIG.4B illustrates a sphere approximation model of the ring model 10′constituted by a plurality of spheres 50 arranged at regular intervalsalong in the ring shape (here, eight spheres 50 are illustrated). Thecenter of each of the eight spheres is on a zx plane. The distancebetween the center and the original point is the same in the eightspheres. The centers of eight spheres are arranged at regular intervalsat 45 degrees on the same circumference about the original point.

First, a case in which a single sphere exists will be considered. Inthis case, it is generally known that, as an influence when the externalmagnetic field is applied to the sphere, a model in which a magneticmoment m [Wb·m] is disposed at the center of the sphere is developed.

$\begin{matrix}{m = \frac{\left( {\mu_{r} - 1} \right)B_{0}V}{1 + {\left( {\mu_{r} - 1} \right)N}}} & \left\lbrack {{Math}.\mspace{14mu} 1} \right\rbrack\end{matrix}$

In the equation, B0 represents the external static magnetic field T(tesla), μr represents the relative permeability, N represents thedemagnetization factor (⅓ in a case of a sphere) and V represents thevolume [m³] of the sphere. The relative permeability μr and the magneticsusceptibility χm are in the following relationships.

μr=1+χm

Here, in order to derive a magnetic field Bm which the magnetic moment mgenerates at an arbitrary point in a space, magnetic potential φ at apoint situated at a distance r[m] from the point at which the magneticmoment m is placed will be considered.

$\begin{matrix}{\Phi = \frac{m \cdot r}{4\; \pi \; \mu_{0}r^{3}}} & \left\lbrack {{Math}.\mspace{14mu} 2} \right\rbrack\end{matrix}$

In the equation, μ0 represents vacuum permeability and m·r represents ascalar product of a vector of m and a vector of r. The generatedmagnetic field Bm can be expressed by a gradient of the magneticpotential φ, and is obtained as Bm=−μ₀ grad φ. When the magnetic momentm placed at the original point is obtained on a polar coordinate withthe m direction as a ground line and is converted into a Cartesiancoordinates, the components of the generated magnetic field Bm areexpressed by the following equations.

$\begin{matrix}{{B_{x} = {B_{A}\cos \; \Phi}}{B_{y} = {B_{A}\sin \; \Phi}}{B_{Z} = {\frac{\mu_{r} - 1}{\mu_{r} - 2} \cdot \frac{{3\; \cos^{2}\theta} - 1}{\left( {r/R} \right)^{3}} \cdot B_{0}}}} & \left\lbrack {{Math}.\mspace{14mu} 3} \right\rbrack\end{matrix}$

The generated magnetic field Bm by the sphere 30 is expressed as afunction of the distance r from the center of the sphere 30 (R: theradius of the sphere). The following equation holds.

$\begin{matrix}{B_{A} = {\frac{\mu_{r} - 1}{\mu_{r} - 2} \cdot \frac{3\; \cos \; \theta \; \sin \; \theta}{\left( {r/R} \right)^{3}} \cdot B_{0}}} & \left\lbrack {{Math}.\mspace{14mu} 4} \right\rbrack\end{matrix}$

Next, the above discussion will be extended to a case in which aplurality of spheres exist. It is assumed that a plurality of spheresare arranged on the zx plane as illustrated in FIG. 4B. The spheres arearranged at regular intervals with the center thereof disposed at thecircumference of the radius d of the original point. When thecoordinates of the center of n spheres are represented by Pi=(Pzi, Pxi),i=0, 1, . . . , n−1, the following equations hold.

$\begin{matrix}{{P_{zi} = {{d\; \cos \; \eta} = {d\; {\cos \left( {\frac{2\; \pi}{n}i} \right)}}}}{P_{xi} = {{d\; \sin \; \eta} = {d\; {\sin \left( {\frac{2\; \pi}{n}i} \right)}}}}} & \left\lbrack {{Math}.\mspace{14mu} 5} \right\rbrack\end{matrix}$

In the above equations, η represents an angle [rad] of the vector Pifrom the z axis.

On the basis of the above discussion, all the generated magnetic fieldby a plurality of spheres may be expressed by the linear sum of theindividual generated magnetic field. That is, the above-obtainedgenerated magnetic field Bm by the single sphere at the original pointis moved in parallel so as to become a magnetic field about Pi and thesum for n spheres is obtained. As the number of spheres 50 is increasedlike 2, 4, 8 and 16 in a range in which the spheres do not overlapmutually, the obtained magnetic field distribution approaches a magneticfield distribution by a toroidal-shaped model.

Exemplary magnetic field distribution calculated in the above-describedprocedure is illustrated in FIG. 5. The generated magnetic field due to16 spheres disposed under the external magnetic field environment hasbeen calculated for a 40-cm cube about the original point, anddistribution of a z-direction component on an xy section has beenplotted. The conditions of calculation are as follows: the staticmagnetic field B0 of the MRI 20 which is the external magnetic field is3.0 [T]; the distance d from the original point to the center of thesphere is 3 [cm]; the radius R of the sphere is 5 [mm]; and the relativepermeability μr of the sphere is 1.02. According to this approximation,in the computer environment used by the inventor, the calculation timeis reduced to about one-several hundreds as compared with a case inwhich the generated magnetic field by the ring model 10′ is calculatedusing the finite element method. The compensated value is fixed if thereis no change in the position and the posture of the actuator 10.

As described above, it is possible to perform the compensation to reducedegradation in the MR image in the case in which an object exists in thebore by calculating an influence which the medical apparatus exerts uponthe magnetic field and transmitting the calculated result to the MRI 20.

Second Embodiment

Since a basic configuration of a second embodiment other than thegeneration method of the compensation information and the degree offreedom of the motion mechanism is the same as that of the firstembodiment, detailed description will be omitted.

FIG. 6 is a block diagram illustrating a configuration of a medicalapparatus in the present embodiment. Unlike the first embodiment, arobotics system having two degrees of freedom is assumed in thisconfiguration. Therefore, two sets (each having one degree of freedomof) actuators 10 a and 10 b, control units 12 a and 12 b, positiondetecting units 1 a and 1 b, and posture detecting units 2 a and 2 bexist, whereby a motion mechanism 11 having two degrees of freedom ismoved. The motion mechanism 11 is a mechanism having at least twodegrees of freedom including vertical movement of a puncture needle 43and rotation of a puncture needle storage unit 42 in a plane including ay-axis. Since the motion mechanism 11 has two degrees of freedom, thepuncture needle storage unit 42 may move like a pendulum, a human body23 may be punctured by the puncture needle 43 from an oblique direction.For example, the medical apparatus of the present embodiment isespecially advantageous in a case in which when the puncture needle 43touches a blood vessel in front of an affected area if the human body 23is punctured vertically.

Similarly to the first embodiment, the system of the present embodimentis also divided into two blocks and the block disposed inside the bore21 (an inner-bore disposed portion 30) is illustrated by a dotted line.Output signals of the position detecting unit and the posture detectingunit are collectively illustrated as a single line for the convenienceof illustration for each set of a and b, and are illustrated as vectorsignals.

In a data storage unit 3, data previously calculated by anothercalculation unit (personal computer) is stored as a look-up table. Thedata is calculated as magnetic field distribution information inaccordance with the position and the posture which the motion mechanism11 of the medical apparatus may take. The data storage unit 3 islarge-capacity semiconductor memory or hard disk. Since compensationinformation is calculated separately, highly precise compensationinformation may be prepared by employing a highly precise analyticmethod. By previously calculating the magnetic field distribution on theassumption that the motion mechanism 11 is placed on an environment of aunit static magnetic field (for example, 1 [T]), the magnetic fielddistribution at this time may be applied to various static magneticfields by multiplying the actual value of the static magnetic field ofthe MRI 20. The step size of the position and the posture which themotion mechanism 11 may take may be the same as that of the side of apixel of the MR image. Alternatively, the step size may be greater thanthat described above and suitable interpolation may be performed forcalculation at the time of actual use. Regarding the mechanism havingtwo degrees of freedom, the magnetic field distribution data about eachof the actuators 10 a and 10 b is stored previously in the data storageunit 3. Then, by calculating the linear sum of each magnetic fielddistribution data by the compensation information calculating unit 4,the magnetic field distribution data for the motion mechanism 11 may beobtained.

Each time various types of information input from each unit (theposition detecting unit 1, the posture detecting unit 2, the datastorage unit 3, the communication unit 5 and the control unit 12) isupdated, the new compensation information is output to the MRI 20 viathe communication unit 5. Since the compensation information which isorigin information other than the above-described interpolationcalculation is previously prepared, the time required for updating datais significantly shorter than that required in the first embodiment.

In the present embodiment, the driving mechanism has two degrees offreedom. However, the driving mechanism may have three or more degreesof freedom.

As described above, by preparing highly precise compensation informationpreviously, real-time performance, i.e., applicability to high-speedimaging sequences of the MRI, is increased and, suitability forautomation of medical practice, such as operation by an MR imagefeedback, is also increased.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

REFERENCE SIGNS LIST

-   -   3 data storage unit    -   4 compensation information calculating unit    -   5 communication unit    -   10 actuator    -   11 motion mechanism    -   12 control unit

What is claimed is:
 1. A medical apparatus comprising: a motionmechanism; an actuator configured to drive the motion mechanism; and acalculator that calculates information on an influence upon an externalmagnetic field by the actuator using data on magnetic susceptibility ofthe actuator, wherein the medical apparatus is configured to generate anMR image based on image data obtained by an MRI apparatus and the dataon the magnetic susceptibility.
 2. The medical apparatus according toclaim 1, wherein the influence in the MR image is decreased.
 3. Themedical apparatus according to claim 1, wherein the information isdistribution information of a magnetic field which the actuatorgenerates in response to an influence of the magnetic field.
 4. Themedical apparatus according to claim 1, wherein the calculator uses aparameter on the MRI apparatus which is received from a communicationinterface.
 5. The medical apparatus according to claim 1, furthercomprising at least one posture detecting unit configured to detect aposture of the actuator, wherein the calculator uses posture informationoutput from the posture detecting unit.
 6. The medical apparatusaccording to claim 1, wherein the calculator is configured to calculatethe information on the influence each time when update of at least onepiece of information input from a data storage is detected and output anupdated result of the MR image.
 7. The medical apparatus according toclaim 1, wherein the actuator is an ultrasonic motor.
 8. The medicalapparatus according to claim 1, wherein the calculator performscalculation which generates information on a generation magnetic fieldby a ring-shaped object using combination of a plurality of spheres. 9.The medical apparatus according to claim 1, wherein the motion mechanismhas two degrees of freedom.
 10. The medical apparatus according to claim1, further comprising a position detecting unit configured to detect aposition of the actuator, wherein the calculator calculates positioninformation output from the position detecting unit.
 11. The medicalapparatus according to claim 1, further comprising a data storage unitin which data on magnetic susceptibility of the actuator device isstored.